OCR A Jun 2014 Paper 2 Q1

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Answer all the questions. This question is about cyclic organic compounds. The table shows some information about cycloalkanes. Cycloalkane Skeletal formula Boiling point / C Cyclopropane Cyclopentane Cyclohexane 33 49 81 (a) These cycloalkanes are members of the same homologous series and have the same general formula. (i) What is meant by the term homologous series?[2] (ii) State the general formula for these cycloalkanes.[1] (iii) Explain the increase in boiling points of the cycloalkanes shown in the table.[2]OCR 2014 Turn over<br />
 (b) The CCC bond angles in cyclohexane are 109.5. State and explain the shape around each carbon atom in cyclohexane. shapeexplanation[2] (c) In the absence of ultraviolet radiation, cyclopropane undergoes an addition reaction with bromine. Suggest the structure of the organic product formed in this reaction. [1] (d) Petrol contains both cyclohexane, C6H12, and hexane. Cyclohexane can be prepared from hexane. (i) Construct the equation for this reaction.[1] (ii) Suggest one advantage of adding cyclohexane to hexane in petrol.[1] (e) Cyclobutane is another cycloalkane. There are several unsaturated isomers of cyclobutane that are alkenes. Two of these isomers are stereoisomers. (i) Explain what is meant by the term stereoisomers.[1] (ii) Draw these two stereoisomers.OCR 2014 [2]<br />
 (f) In the presence of ultraviolet radiation, cyclohexane reacts with bromine. A mixture of cyclic organic compounds is formed, including C6H11Br. (i) Complete the table below to show the mechanism of the reaction between bromine and cyclohexane to form C6H11Br. Include all possible termination steps in your answer. Step Initiation Propagation EquationTermination(ii) The initiation step involves homolytic fission. Explain why the initiation step is an example of homolytic fission. [5][1] (g) The reaction between cyclohexane and bromine in (f) also forms C6H10Br2. (i) Write an equation, using molecular formulae, for the reaction of cyclohexane and bromine in the presence of ultraviolet radiation to form C6H10Br2.[1] (ii) Name one of the structural isomers of C6H10Br2 formed in the reaction between cyclohexane and bromine.[1]OCR 2014 [Total: 21] Turn over<br />

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